I have a problem with my Pentax K100d that I would be gratful if anyone could offer any advice on. The problem is that in any mode requiring auto exposure, the camera massivly underexposes to the extent where output is just black. For example, in low light conditions where I would expect shutter speeds of say 1/20 or slower, it is selecting 1/500 - 1/2000. Intermittently however it works correctly. Manual exposure works fine. This occurred a while ago and it was sent back to pentax who seemed to fix the problem (albeit they kept the thing for 2 months). The service docket said something like exposure reset or re-calibrated. After that things were ok again for a while but the problem has started again. The camera is still under warrantee (just) and so I intend to send it back again but my concern is that pentax will do a temporary fix again but that the camera has a more serious fault somewhere. Can anyone suggest what the problem might be? Should I be insisting on a replacement? Can the exposure be user reset/re-calibrated? many thanks for any thoughts or suggestions.